Control system



June 2 3, 1942., J. WEBER CONTROL SYSTEM Filed May 14, 1941 2 Sheets-Sheet 1 L. mb N6 N WW ma/vw 0,

June 23, 1942. J, WEBER CONTROL SYSTEM Filed May 14, 1941 2 Sheets-Sheet 2 lNvl-:NTOR foe Weber? Patented June 23, 1942 CONTROL SYSTEM Joe Weber, Irwin, Pa., assignor to Westinghouse Electric & Manufacturing Company, Pittsburgh, Pa.,.a corporation of Pennsylvania Application May 14, 1941,`Serial No. 393,391

7 Claims.

My invention relates, generally, to control systems, and more particularly, to a control system for a steel strip rolling mill and the like.

It has been found that, with all other conditions remaining constant, the amount of reduc- Y tion of a strip of steel as it passes through a strip mill varies with the speed at which the reducing rolls are driven. Thus, when the mill is accelerated and decelerated from and to the speed required for threading the mill, the strip pro.

duced is of larger gauge than that produced while vthe mill is running at normal speed.

An object of the invention is to provide a control system for a strip rolling mill which shall function to compensate for the variations in strip gauge when the speed of the mill is varied.

Another object of the invention is to provide a control system for a strip rolling mill which shall function to automatically vary the tension on a strip in a strip rolling mill in accordance with variations in the speed of the mill to thus compensate for strip gauge variations due to the speed variations of the mill.

A further object of the invention is to provide a control system for a strip rolling mill which shall function to automatically control the tension and/ or the screw-down setting of the` mill in accordance with the speed of the mill to thereby compensate for strip gauge variations occasioned by variations of the speed of the mill.

Another object of the invention is to provide a control system for a work device which acts upon a length of material as it passes through the deice which shall function to control the tension on the length of material as it passes through the Work device in accordance with the speed of travel of the length of material.

A further object of the invention is to provide a control system for a strip rolling mill which shall function to automatically control the tension on a length of material as it passes through the mill within predetermined tension limits and which shall function to vary the spacing of the reducing rolls of the mill when these predetermined tension limits are reached.

These and other objects and advantages of the invention .will be apparent from the following detailed description taken in connection with the accompanying drawings, in which like reference characters designate similar elements and in which:

Figure l is a control diagram fora strip rolling mill embodying the principal features of a pre ferred embodiment of the invention;

Fil

Fig. 2 is a control diagram for a strip rolling mill embodying the principal features of another Iembodiment of the invention.

In the embodiment of the invention shown in Fig. 1, a tensioning roller I Il is made to bear upon a strip I2 as it passes between the roll stands I4 and I6 of a strip rolling mill. The tensioning roller II) maybe actuated by a pressure uid operated piston I8 and a regulator 20 controls the drive motor 22 for the roll stand I4 to keep the tensioning roller l0 within predetermined limits of strip deflection. A fluid pressure regulating valve 24 controls the fluid pressure acting upon the piston I8 and thereby controlsthe tension on the strip. A solenoid 26 may be variably energized by a circuit including a variable resistor 28 to vary the iluid pressure acting on the piston I8 to thereby vary the lstrip tension. The operation of the tensioning roller III to tension the strip, the regulator 2l), and the regulating valve 24 under the influence of the solenoid 26 is described in the patent to W. G. Cook, No. 2,223,718, issued December 3, 1940, and reference is made to this patent for a detailed description of the operation of these elements.

A second solenoid 30 is disposed in operative relation with the regulating valve 24 and this solenoid is energized in accordance with the speed of the drive motor 32l for the roll stand I6 to thus vary the strip tension in accordance With the speed of the mill.

A screw-down control system 34 is also controlled in accordance with the speed of the mill to thereby vary the spacing of the reducing rolls of the roll stand I6 in accordance with variations in the mill speed.

In the embodiment of the invention shown in Fig. 2, the screw-down setting of the roll stand I6 is controlled by a fluid pressure responsive con. trol device 36 in accordance with the iluid pressure acting to tension the strip I2 and acts to control the screw-down setting or' the roll stand i6 and the tension on the strip when the strip tension reaches predetermined limits.

Referring again to Fig. 1 for a more detailed l conductor 54 to the other terminal of the generator 38.

The solenoids 26 and 30 are disposed to oppose each other so that increased energization of the solenoid 26 tends to increase the fluid pressure acting upon the piston I8 and increased energization of the solenoid 30 tends to decrease the fluid pressure acting upon the piston |8. Thus as the speed of the mill increases, the energization of the solenoid 30 Will be increased to decrease the fluid pressure on the piston I8 and to thereby decrease the tension on the strip I2. In this way, the reducing forces on the strip lI2 may be made to remain substantially constant since the increased reduction due to the increased speed of the mill will be compensated for by decreased strip reducing forces due to the decrease in the tension of the strip as it passes through the mill. The variable resistor 52 may be adjusted as desired to provide whatever degree of compensation is necessary.

The mechanism 56 for adjusting the screwdown setting of the mill is driven by a motor 58 through a shaft 60. The motor 58 has a eld winding 62 which may be selectively energized by relays 64 and 66 to cause the motor 58 to'rotate in the desired direction to either increase or decrease the spacing of the reducing rolls of the mill stand I6. The eld winding 62 of the motor 58 may be energized by the relay 64 to cause the screw-down setting of the mill to' increase the spacing of the reducing rolls to thereby give decreased reduction of the strip |2 in a circuit extending from a conductor X, which may be connected to one terminal of any suit-l able source of direct current power, through a conductor 68, contact element I of the relay 64, a conductor 12, the eld Winding 62, conductors '|4 and 16, contact element 18 of the relay 64 and conductors 80 and 82 to the conductor Y, which may be connected to the other terminal of .the source of direct current power. The motor 58 may be caused to rotate in the opposite direction by providing an opposite polarity of energization for the field winding 62 as the result of the energization of the relay 66 in a circuit which extends from the conductor X through conductors 68 and 84, contact element 86 of the relay 66, the conductor 14, the field winding 62, conductors 'I2 and 88, contact element 90 of the relay 66 and conductors 80 and 82 to the conductor Y.

A solenoid 92 is connected to be energized by the pilot generator 38 in a circuit which extends from one terminal of the generator 38 through a conductor ||8, the winding of the relay 66 and conductors I I6 and 82 to conductor Y. The spaced contact elements |08 and I I0 are mounted upon a sleeve |20 having screw-threaded engagement with a shaft |22 which is driven by the shaft 60 through gear members |24 and |26.

Thus when the speed of the mill I6 increases, the output potential of the pilot generator 36 will increase which will, in turn, cause increased energization of the solenoid 92 and the engagement of the contact elements |06 and |08. This Will cause the relay 64 to beenergized to, in turn, cause the motor 58 to drive the screw-down mechanism 56 in a direction to decrease the screw-down setting or increase the reducing roll spacing of the mill stand I6 to thus compensate for the increased reduction of the strip I2 due to the increased. speed of the mill I6. The variable resistor |00 may be adjusted as desired to provide any desirable compensation by variation of the screw-down setting. The circuit control devices 48 and 96 which control the circuits of the solenoids and 92 may be opened or closed as desir ed to provide either tension compensation or screw-down compensation or both with variations of speed in the mill.

conductors 44 and 94, a circuit control device 96,

a conductor 98, a variable resistor |00, a conductor |02, the winding of the solenoid 82, and conductors |04 and 54 to the other terminal of the pilot generator 38. The solenoid 92 is thus energized in accordance with thespeed of the mill motor 52 and actuates a movable contact element |06 which is disposed to engage contact element |08, or I I0, when an increase or decrease of the energization of the solenoid 92 occurs. The relay 64 is energized by the engagement of the contact elements |06 and |08 in a circuit which extends from the conductor X through conductor ||2, contact elements |06 and |08, a conductor ||4` the winding of the relay 64 and conductors IIG and 82 to the conductor Y.

A similar circuit for energizing the relay 66 is controlled by the contact elements |06 and |I0 and extends from the conductor X through the conductor ||2, contact elements |06 and |I0,

In the embodiment of the invention shown in Fig. 2, the pilot generator 38 is connected to energize the solenoid 30 in a circuitwhich extends from one terminal of the generator 38 through a conductor |28, a variable resistor |30,` a conductor |32, the winding of the solenoid 30, a conductor |34, a variable resistor |36, and a conductor I 38 to the other terminal of the generator 38. This circuit will function to Vary the tension applied to the strip I2 by the tension roll I0 in inverse proportion to the speed of the mill 32.

The pressure responsive device 36 is connected to the conduit |40, which extends between the regulating valve 24 and the piston I8, to be responsive to the fluid pressure acting upon the piston I8 and to be energized, therefore, in accordance with variations in theA tension on the strip |2 which, in turn, is a function of the speed of the motor 32 and the mill stand I6. The pressure responsive device 36 is disposed to actuate a movable contact element |42 and fixed adjustable contact elements |44 and |46 are disposed in the path of travel of the contact element |42 to be engaged thereby upon predetermined increase or decrease of the fluid pressure acting to tension the strip. The contact element |42 and cooperating contact elements |44 and |46 are disposed to control relays 64 and 66 to thereby control the screw-down motor 58 and the screwdown mechanism 56 as described hereinbefore in the explanation of the operation of the embodiment of the invention shown in Fig. 1. The variable resistor |36 is connected to be actuated by a shaft |22 which, in turn, is actuated by the shaft 60 through the gear members |24 and |26.

In the operation of the system shown in Fig. 2, any change in the speed of the mill I6 will cause a change in the uid pressureI acting on the piston |8 and will, therefore, cause a change in the tension on the strip |2 and when this tension is changed to the extent that the contact element |42 engages either the contact element |44 or |46, the screw-down setting will be changed accordingly and the actuation of the screw-down apparatus will, in turn, actuate the variable resistor |36 to change the fluid pressure acting on the piston |8. Thus, upon an increase in the speed of the mill I6, the tension on the strip I2 will be decreased. When there is suicient decrease in tension on the strip I2 to permit the contact elements |42 and |46 to engage, the screw-down setting of the mill stand I4 will be decreased and this decrease in the screw-down setting will so actuate the variable resistor |36 as to decrease the energization of the solenoid and thereby increase the fluid pressure sufliciently to cause the contact element |42 to be disengaged from the contact element |46. In a similar manner, a decrease in speed of the mill will cause a corresponding increase in the tension on the strip |2 until the contact element |42 engages the contact element |44 at which time the screw-down setting of the reducing rolls in the mill stand I6 will be Varied to decrease the spacing of the reducing rolls and the variable resistor |36 will be so actuated as to increase the fluid pressure to' disengage the contact elements |42 and |43.

Thus compensation for the variation in the strip thickness due to variations in the speed of the mill will be provided by variations in the tension on the strip |2 between predetermined limits of tension as determined by the setting of the contact elements |44 and |46 and compensation for variations in speed beyond the speed at which these contact elements function to vary the screw-down will be provided by the proper manipulation of the screw-down setting of the mill. The variable resistor |30 may be adjusted as desired to provide any desired degree of energization of the solenoid 30.

controlling the force applied to said actuating means to therebycontrol the tension on the strip, and means responsive to the force applied by said force applying means for controlling the screw-down setting of the mill.

. plying means.

'Ihus it will be seen that I have provided a control system for a work device which acts upon a length of material as it passes through the Work `device which shall function to control the forces acting upon the length of material in response to the speed of travel of the length of material through the work device.

In compliance with the requirements of the patent statutes, I have shown and described herein the preferred embodiments of my invention. It is to be understood, however, that the invention is not limited to the precise constructions shown and described but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustra,- tive of the principal features of my invention.

I claim as my invention:

l. In a control system for a strip rolling mill, means responsive to variations of the speed of the mill, and means controlled by said speed responsive means for varying the screw-down setting of the mill to thereby compensate for variations in the reduction of the strip due to changes in the speed of the mill.

2. In a control system for a strip rolling mill, means responsive to variations of the speed of the mill, and means controlled by said speed responsive means for varying the tension on the strip and the screw-down setting of the mill as the strippassesthrough the mill to thereby compensate for variations in the reduction of the strip due to variations in the speed of the mill.

3. In a control system for a strip rolling mill, means subjecting a strip of material to tension as it passes througlrthe mill, force applying-- means for actuating said strip tensioning means, means responsive to the speed of the mill for 5. In a control system for a strip rolling mill, means engaging a strip of material as it passes through the mill to thereby subject the strip to tension, pressure duid operated means for causing said means to subject the strip to a tension which is a function of the iiuid pressure acting on the pressure fluid operated means, means responsive to variations of the speed of the mill, and means whereby said speed responsive means controls the fluid pressure acting on the pressure fluid actuated means to thereby vary the strip tension in accordance with variations of the speed of the mill.

6. In a control system for a strip rolling mill, means engaging astrip of material as it passes through the mill to thereby subject the strip to` tension, pressure duid operated means for causing said means to subject the strip to a tension which is a function of the uid pressure actingl on the pressure iluid operated means, means responsive to the speed of the mill, means whereby said speed responsive means controls `the uid pressure acting on the pressure iiuid actuated means to thereby vary the strip tension in accordance with the speed of the mill, means for varying the spacing of the reducing rolls of the mill, and means responsive to the uid pressure acting on the pressure fluid actuated means for controlling said reducing roll spacing varying means.

7. In a control system for a strip rolling mill, means for engaging a strip of material as it passes through the mill to thereby subject the strip to tension, pressure fluid operated means for causing said bearing means to subject the strip to a tension which is a function of the fluid pressure acting on the pressure fluid operated means, means responsive to the speed of the mill, means whereby said speed responsive h means controls the fluid pressure acting on the pressure fluid actuated means to thereby vary the strip tension in accordance with the speed of the mill, means for varying the spacing of the reducing rolls of the mill, means responsive to the iiuid pressure acting on the pressure uid actuated means for controlling said reducing roll spacing varying means, and means responsive to the actuation of said roll spacing varying means for varying the iiuid pressure acting on said pressure iiuid actuated means.

JOE WEBER. 

